Method to increase wear resistance of a tool or other machine component
A layer system in particular for tools or machine components operated under insufficient lubrication or under dry operation conditions, is proposed, which system, starting from the base body, comprises a hard substance layer system, subsequently a metallic layer and finally a slide layer system, the last mentioned preferably made of Carbide, in particular of Tungstencarbide or Chromiumcarbide and dispersed Carbon.
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The present invention starts from the need to coat tools, and thereby particularly cutting tools or form tools with a base body of metal, thereby in particular of HSS or of tool steel or of hard metal, in such a manner, that they are particularly suitable for dry processing operation or for operation under minimum lubrication (shortage lubrication) etc.
From the solution of this problem and according to the present invention there results a protection coating technique, which is suitable also for other tools and mechanical components, when they are used with little or no lubrication and/or under a high surface loading.
Under ecological and under economical considerations, the operation of tools, in particular of cutting tools and of form tools under minimum lubrication conditions is highly interesting. Under economical aspects it has to be noted that the costs for cooling lubricant, in particular for cutting tools, are substantially higher than for the tool itself. By applying cooling lubricant in the contacting area of tool and workpiece, chips are washed out and heat is dissipated, furthermore a cleaning and corrosion-preventing effect is reached.
There exists an increasing and substantial need to quit with the use of conventional amounts of cooling lubricant, as e.g. of 300 to 4000 litres per hour, for a chipping tool processing, and to drastically reduce that amount to e.g. only 6 to 70 ml per hour for the equal operations.
This leads to a highly sophisticated task, on the one hand, with respect to forming of the tools, on the other hand, with respect to surface treatment applied to such tools and mechanical components. The present invention addresses the last mentioned task.
In the context of the aforementioned problem the task mentioned above is resolved by proposing a tool or mechanical component of the kind mentioned in the generic part of claim 1 at which, according to the invention and following the characterising part of claim 1, the hard material coating system comprises at least one hard material layer made of a material selected from the group of Nitrides, Carbides, Oxides, Carbonitrides, Oxinitrides, Oxicarbonitrides of at least one metal, and further an intermediate layer is provided immediately between the mentioned at least one hard material layer and—propagating in direction from the inside of the base body towards its outside—before the slide layer system, which intermediate layer is made of the same at least one metal, which is present in the at least one hard material layer of the hard material layer system.
It is known from the U.S. Pat. No. 5,707,748 of the same applicant as the present application to deposit a hard material layer system onto the base body of a tool, directly followed by a slide protection layer system. As materials for the hard material layer system metal Carbides, metal Nitrides, metal Carbonitrides or combinations thereof have been proposed, as materials for the slide protection layer system materials based on Carbon, such as especially Tungstencarbide with dispersed Carbon, WC/C.
The known coating has been used with the principal target of increasing the etch life of cutting tools.
The present invention starts from the finding that this known coating technique can be used to fulfil the extreme requirements underlying the problem to be solved in respect to the tools or mechanical components, in particular to cutting tools, if the known overall layer system is construed as proposed by the present invention, in particular by means of inventively providing the metallic intermediate layer.
The tool or mechanical component according to the present invention and according to one of the claims 1, 32, 33, 34, the manufacturing method according to the present invention according to claim 21, and the system according to the present invention according to claim 31 and their preferred embodiments according to the claims 2 to 20, and 22 to 30 respectively will be further explained by way of examples referring to drawings, as well as to Experiments. The figures show:
In
On a base body 1 made of a metal, thereby preferably of HSS or of a tool steel or a hardened steel or a hard metal, a hard material layer system 2 is deposited which comprises at least one hard material layer 2a or which consists of at least one hard material layer 2a which latter is formed of a material selected from the group Nitrides, Carbides, Oxides, Carbonitrides, Oxinitrides, Oxicarbonitrides of at least one metal.
On the hard material layer system 2 a metallic intermediate layer 3 is deposited, which consists of the same at least one metal which is present in the aforementioned hard material layer 2a of the hard material layer system 2. Thereby, for a hard material layer system 2 with several layers, the mentioned hard material layer 2a directly lies at the intermediate layer 3 as is shown by dashed lines in
A slide layer system 4 lies above the intermediate layer 3. This slide layer system 4 again comprises at least one slide layer 4a or consists of a slide layer 4a, whereby in the case of a multi-layer slide layer system, as represented in
The metal used for the hard material layer system 2 and in particular for the mentioned at least one layer 2a is preferably Titanium, Chromium, Hafnium, Zirconium or Aluminum, preferably two of these metals, particularly preferred Ti and Al and/or Cr and Al. Thereby, said layer 2a preferably consists of TiAlN, CrAlN or CrN, especially preferred of TiAlN or CrAlN.
The slide layer system, and thereby in particular its at least one layer 4a, is preferably formed from a Carbide of at least one metal of the group IVb, Vb and/or VIb and/or of Silicon and/or of Boron, thereby preferably of Tungstencarbide, Chromiumcarbide or Titaniumcarbide besides the dispersed Carbon which is incorporated in the slide layer 4a.
Preferred Layer Structure
In
Preferably, between the mentioned at least one layer 4a of the slide layer system 4 and the intermediate layer 3 there is provided a layer 4b at the slide layer system 4, which layer 4b substantially exclusively consists of the metal Carbide. Dispersed Carbon to a significant amount is only provided in the layer 4a, and if not Molybdenedisulfide or Molybdenediselenide is used. The slide layer system 4 has preferably a somewhat smaller thickness than the hard material layer system 2.
Layer Transitions
Considered at the minimal configuration according to
In the slide layer system 4, the metal Carbide concentration MeGSC, and as represented at (c), can be kept constant in the at least one slide layer 4a, or the concentration, the content of metal Carbide, can be—preferably—decreased stepwise or continuously, towards the outside, as is represented schematically at (d).
At the preferred embodiment according to
In the slide layer system 4, preferably a practically 100% MeGSC-concentration is provided in the layer 4b, which concentration decreases abruptly or in steps, thereby preferably continuously towards the outside, due to the additional dispersed Carbon, as represented at (d) of
Preferred Layer Structure of Today
In
If an intermediate layer 2b is provided according to
If layer 4b is provided according to
In the following table I five basic embodiments with hard material layer 2a or 2 respectively, intermediate layer 3 and slide layer 4a or 4 respectively are shown. The numbers Nr. 1 to Nr. 5 thereby accord with the priority of preference, at least today.
Thereby, in some cases the slide layer 4 or 4a may consist or comprise Molybdenedisulfide or Molybdenediselenide.
Further, it must be pointed out that the present invention may also be used in context with hardened steel substrates, which may have advantages in tool applications with very high mechanical strength per surface area.
The slide system 4 may additionally comprise a terminating Carbon layer, especially preferred of a-c:H or DLC without substantial additive of a metallic component. With respect to the definition of a-c:H we refer to René A. Häfler, “Oberflächenund Dünnschicht-Technologie” (Surface and thin film technology), Springer; Berlin, Heidelberg, New York, London, Paris, Tokyo, 1987, Part I “Beschichtung von Oberflächen” (Coating of surfaces), pp. 169 to 172.
With respect to DLC (diamond-like carbon) we refer to ASM handbook, third printing 1999, pp. 553, 554.
Deposition of this layer may thereby be performed by means of plasma-activated Carbon containing gas, by sputtering or evaporation of at least one Carbon target applied in the respective coating chamber. Adhesion of such layer may thereby be increased by applying a DC or AC or, superimposed, AC and DC, thereby especially of a pulsed bias to the substrate relative to the target.
It goes without saying that for all deposition steps used within the present invention, plasma activation may be done by glow discharge, by high current low-voltage arc discharge, by means of hollow cathode etc.
Preferred Thickness Dimensions
Hard substance Layer Systems:
-
- The hard substance layer system 2, especially if, in its preferred embodiment according to
FIG. 5 , made of TiAlN or CrAlN, has a thickness dHS as follows:
0,1 μm≦dHS≦6 μm, - thereby preferably
2 μm≦dHS≦5 μm.
Metal Intermediate Layer 3: - The metal intermediate layer 3, in particular if consisting of TiAl or CrAl according to
FIG. 5 , has a thickness dZW1:
0,01 μm≦dZW1≦1 μm, - preferably
0,1 μm≦dZW1≦0,5 μm.
- The hard substance layer system 2, especially if, in its preferred embodiment according to
Slide layer system 4:
-
- The slide layer system 4 has, in particular in the preferred embodiment according to
FIG. 5 , a thickness dGL as follows:
0,1 μm≦dGL≦6 μm, - thereby preferably
1 μm≦dGL≦3,5 μm.
- The slide layer system 4 has, in particular in the preferred embodiment according to
If according to
0,01 μm≦dGL1≦1 μm,
preferably
0,1 μm≦dGL1≦0,5 μm
0,1 μm≦dGL2≦5 μm
preferably
1 μm≦dGL2≦3 μm.
Intermediate Layer 2b:
If provided, the further metal intermediate layer 2b is construed with a thickness dZW2 as follows:
0,01 μm≦dZW2≦1 μm,
thereby preferably
0,1 μm≦dZW2≦0,5 μm.
Coating Method
-
- Hard Material System
The hard material layer system with, as was mentioned, the at least one hard material layer, preferably of CrAlN or TiAlN, can be produced by reactive sputtering, thereby preferably by reactive magnetron sputtering or by reactive cathodic arc evaporation. Preferably, it is produced by reactive cathodic arc evaporation. Thereby, highly dense ion plated structures are realised without pores and with steady transitions to the subsequent layer systems and to the base body material respectively.
-
- Intermediate Layer 3
The intermediate layer 3, made of the same at least one metal as contained in the hard material system 2 with the at least one layer 2a, according to
Slide Layer System 4
The slide layer system is realised by cathodic arc evaporation or, preferably, by sputtering of a target, in particular by magnetron sputtering of a target, directly or, for the embodiment according to
Compared to the also possible reactive sputtering of metallic targets, sputtering of Carbide targets has the advantage that overall a higher C-content in the layer being deposited is reached. A matrix of amorphous Carbon with nano-crystalline Carbide corns is created. By cyclically exposing the workpieces more and less to the at least one Carbide source, in particular to the at least one Carbide sputtering source, a laminar microstructure of layers with changing ratio of dispersed Carbon and Carbide is created, highly advantageous for a slide layer system. Gradual transitions, as schematically represented in the
Pre-processing of the Base Body Surface
It is advised to plasma etch the base body surface before coating, in particular using a low-voltage discharge. In the following table the variables of the decisive process parameters as applied are listed for a coating according to the invention as of
System i.e. Apparatus Configuration
In
It is evident that according to the preferred method for deposition of the hard material layer system first only the arc evaporation sources 14 are reactively operated, preferably under inlet of reactive gases containing Nitrogen, and that for the deposition of the metallic intermediate layers the reactive gas flow is stepwise or continuously reduced with unit 26, and that further for deposition of the slide layer system the sputtering sources 15 are operated preferably with carbidic targets under the inlet of gas containing Carbon, controlled by the unit 26. The layer transitions are realised, as desired, by corresponding changes of the gas flows and/or of the evaporation and sputtering power respectively. For deposition of the slide layer system, during which the arc evaporation sources 14 are disabled, one obtains, as was already mentioned, cyclic phases during which the workpieces 20 are more exposed to the sputtering sources 15 (left position of the workpieces) and are then more distant from the sources, thereby still exposed to the influence of Carbon gas. Thereby, the preferred laminar structure is obtained for the slide layer system as was mentioned.
Results
Especially by the combined coating of sputtering and of arc evaporation, a dense, hard coating having extraordinary sliding and adhesion abilities is obtained according to the present invention.
Drilling results are shown in
-
- Feed vc=20 m/min
- f=0,12 mm.
Pressurised air of only 1 bar was used. It must be emphasised that the drills used were not formed for dry processing, as performed, but that the only point of this experiment was to compare the behaviour of the different coating systems. On the vertical axis of
It can be seen that—according to the bar A—substantially better results have been reached with the drills coated according to the invention than with the drills—according to the bar B—which have only been coated with a TiAlN hard material coating or than with drills with a hard material coating made of TiN and having a subsequent slide layer coating of Tungsten-carbide and dispersed Carbon—bar C—or, referring to bar E, than with drills with a hard material coating TiN. The coating of the drills according to bar C substantially corresponds to the coating according to the U.S. Pat. No. 5,707,748.
Therefrom, it can clearly be seen that the tools i.e. the drills coated according to the invention have excellent dry processing characteristics with respect to etch life.
In
It can be seen, first by comparison of the courses (a2) and (b2), that the necessary torque to keep a constant rotation speed, at (a2) for drills with known hard material coating, substantially increases at a certain drilling depth, which leads to torque peaks according to (a1), whereas no substantial increase of the drive torque necessary is observed for drills coated according to the invention, as can in particular be seen from (b2), even at relatively large drilling depths. This shows the excellent sliding characteristics of the drills coated according to the invention, which proves, in combination with the results according to
In
The workpiece drilled was steel AISI H11 50HRc.
The cutting parameters were:
-
- vc: 80 m/min. (262 sfm)
- f: 0.12 mm/rev. (0.005 ipr)
blind holes, 15 mm deep (0.6 in), dry drilling, compressed air cooling.
The columns represent the number of holes achieved.
Tool (Inventive):
HSS drill, diameter 6 mm (0.24 inch), coated with the same basic layer system No. 2 of Table I.
Workpiece: Steel AISI D3
Cutting parameters:
vc: 20 m/min. (65 sfm)
f: 0.12 mm/rev. (0.005 ipr)
blind holes of 15 mm (0.6 in) depth.
Dry drilling, compressed air cooling.
Again, the columns represent the resulting number of holes.
In
Tool (Inventive):
HSS tap, M8, coated with a system according to table I Nr. 2
further inventively coated tool, comprising the system:
-
- a hard material layer of TiN
- an intermediate layer of Ti
- a slide layer of WC/C.
Workpiece: Steel AISI 4142 (DIN 42) CrMo4
Cutting Parameters:
Vc: 15 m/min. (49 sfm)
In
Tool:
Broach, HSS (M42)
25×7×180 mm, coated with the system Nr. 2 of the above mentioned table I.
Workpiece: Hardened steel, 51 HRc
Cutting Parameters:
vc: 6 m/min. (20 sfm)
Strobe: 25 mm (1 in)
Further, turning experiments with cutting plates of HSS coated with the above mentioned Nr. 2 system were performed. The workpiece was of titanium alloy, as for medical applications and turning was performed under emulsion cooling. With the cutting plates inventively coated as mentioned, the standing lifetime of the tools was three times longer than that of tools coated with just the hard material layer TiCN.
From the results it may be seen that the extremely good sliding abilities of the combined layer system according to the invention most effectively prevent cold shutting and build-up-etching, which results on one hand from the very low friction coefficient of the slide layer system 4 and thereby the extremely good start-up conditions.
On the other hand it results from the high hardness and the good supporting effect of the hard material layer system 2. Thereby, and in the start-up phase the loaded surfaces of the tool are practically “polished” by the leaving chip. The practically “polished” surfaces result in a significant lowering of the working temperature, so that e.g. during hole-drilling realised with inventive tools as according to the
Thus, a coating system is proposed by the present invention, which system has besides excellent wear and tear characteristics excellent sliding characteristics and excellent adhesive power characteristics. It is in particular suitable, as mentioned, for tools and machine components, for tools in particular for cutting tools and forming tools which are operated under minimum lubrication conditions or even under dry operation conditions.
Claims
1. Tool or machine component, comprising:
- a base body made of metal or made of hard metal;
- viewed in a direction from the base body towards an outside and at least along a part of the base body's surface, a hard material layer system having, as an outermost layer, a hard material layer, directly followed by an intermediate layer, directly followed by a sliding layer system;
- wherein said hard material layer made of at least one material from the group of Nitrides, Carbides, Oxides, Carbonitrides, Oxinitrides, Oxicarbonitrides of at least one metal, and said intermediate layer is of said at least one metal.
2. Tool or machine component according to claim 1, wherein said sliding layer system includes at least one layer comprised of a Carbide of at least one metal with dispersed Carbon, MeC/C.
3. Tool or machine component according to claim 1, wherein said sliding layer system comprises at least one layer of at least one of Molybdenedisulfide and of Molybdenediselenide.
4. Tool or machine component according to claim 1, wherein said sliding layer system comprises at least one layer which substantially consists of Carbon.
5. Tool or machine component according to claim 4, wherein said at least one layer of said sliding layer system is an uppermost layer of said sliding layer system.
6. Tool or machine of claim 4, wherein said at least one layer of said sliding layer system substantially consists of a c:H or of diamond-like Carbon.
7. Tool or machine component according to claim 1, wherein said hard material layer comprises at least one of the metals Titanium, Chromium, Hafnium, Zirconium, Aluminium.
8. Tool or machine component according to claim 1, wherein said hard material layer comprises at least two of the metals Titanium, Chromium, Hafnium, Zirconium, Aluminium.
9. Tool or machine component according to claim 1, wherein said hard material layer comprises at least one of TiAl and CrAl.
10. Tool or machine component according to claim 1, wherein said hard material layer consists of one of TiAlN, CrAIN, CrN.
11. Tool or machine component according to claim 1, wherein said sliding layer system includes a layer which comprises a carbide of at least one of Silicon, Boron, a metal of the groups IVb, Vb, VIb.
12. Tool or machine component according to claim 11, wherein said layer comprised of at least one of Silicon, Boron, and a metal of the groups IVb, Vb, VIb is provided directly on said intermediate layer.
13. Tool or machine component according to claim 1, wherein said sliding layer system comprises a layer which comprises at least one metal of Tungstencarbide, Chromiumcarbide, Titaniumcarbide.
14. Tool or machine component according to claim 13, wherein said layer comprised of at least one metal of Tungstencarbide, Chromiumcarbide, and Titaniumcarbide is provided directly on said intermediate layer.
15. Tool or machine component according to claim 1, wherein said sliding layer system consists of one layer.
16. Tool or machine component according to claim 1, comprising a further intermediate layer between said base body and said hard material layer system.
17. Tool or machine component according to claim 16, wherein said further intermediate layer is of metal.
18. Tool or machine component according to claim 17, wherein said metal is said at least one metal.
19. Tool or machine component according to claim 1, wherein a concentration of dispersed Carbon in said sliding layer system and viewed in a direction from the base body towards the outside varies stepwise or continuously.
20. Tool or machine component according to claim 19, wherein said concentration increases in said direction.
21. Tool or machine component according to claim 1, wherein a concentration of dispersed Carbon in said sliding layer system is substantially constant along a thickness portion of said sliding layer system.
22. Tool or machine component according to claim 1, wherein said hard material layer transits, viewed in a direction from said base body towards the outside, with a stepwise or with a continuously increasing concentration of said at least one metal into said intermediate layer.
23. Tool or machine component according to claim 17, wherein said further intermediate layer transits, viewed in a direction from said base body towards the outside, with a decreasing concentration of said metal into said hard material layer system.
24. Tool or machine component according to claim 1, wherein said sliding layer system comprises an innermost layer which consists substantially of a Carbide.
25. Tool or machine component according to claim 1, wherein said hard material layer system has a thickness dHS in which:
- 0.1 μm>dHS>6 μm.
26. Tool or machine component according to claim 25, wherein said hard material layer consists of one of TiAIN and CrAlN.
27. Tool or machine component according to claim 25, wherein:
- 2 μm>dHS>5 μm.
28. Tool or machine component according to claim 1, wherein said intermediate layer has a thickness dZW1 in which:
- 0.01 μm>dZW1>1 μm.
29. Tool or machine component according to claim 28, wherein said intermediate layer consists of one of TiAl and of CrAl.
30. Tool or machine component according claim 28, wherein
- 0.1 μm>dZW1>0.5 μm.
31. Tool or machine component according to claim 1, wherein said sliding layer system has a thickness dGL in which
- 0.01 μm>dGL>6 μm.
32. Tool or machine component according to claim 31, wherein said sliding layer system comprises at least one of WC, CrC, TiC.
33. Tool or machine component according to claim 31, wherein:
- 1 μm>dGL>3.5 μm.
34. Tool or machine component according to claim 31, wherein said sliding layer system comprises an innermost first layer of a Carbide which has a thickness dGL1 in which:
- 0.01 μm>dGL1>1 μm.
35. Tool or machine component according to claim 34, wherein:
- 0.1 μm>dGL1>0.5 μm.
36. Tool or machine component according to claim 34, wherein said sliding layer system comprises has a second layer of a Carbide and of dispersed Carbon.
37. Tool or machine component according to claim 34, wherein said Carbide is one of WC, CrC, TiC.
38. Tool or machine component according to claim 36, wherein said Carbide of said second layer and said Carbide of said innermost first layer are the same.
39. Tool or machine component according to claim 36, wherein said second layer has a thickness dGL2 in which:
- 0.1 μm>dGL2>5 μm.
40. Tool or machine component according to claim 39, wherein:
- 1 μm>dGL2>3 μm.
41. Tool or machine component according to claim 16, wherein said further intermediate layer has a thickness dZW2 in which:
- 0.01 μm>dZW2>1 μm.
42. Tool or machine component according to claim 41, wherein said further intermediate layer consists of one of TiA1 and CrA1.
43. Tool or machine component according to claim 41, wherein:
- 0.1 μm>dZW2>0.5 μm.
44. Tool or machine component according to claim 1, wherein said base body consists of one of high speed steel, tool steel, hardened steel.
45. Tool or machine component according to claim 1, wherein the tool or machine component is a cutting tool or forming tool for the use under deficient lubrication up to dry use.
46. Tool or machine component according to claim 1, wherein the at least a portion of said sliding layer system consists of a laminar structure with first layers and second layers, said first layers having higher Carbon content than said second layers and said second layers having higher Carbide content than said first layers.
47. Tool or machine component according to claim 1, wherein said sliding layer system has an innermost layer of one of Tungstencarbide, Chromiumcarbide, Titaniumcarbide.
48. Tool or machine component according to claim 1, wherein said sliding layer system has an uppermost layer which substantially consists of a c:H or of diamondlike Carbon.
49. Tool or machine component, comprising:
- a base body of a metal or of a hard metal, and
- viewed in a direction from said base body towards an outside and at least along a part of the base body's surface, a hard material layer system having, as an outermost layer, a hard material layer, directly followed by an intermediate layer, directly followed by a sliding layer system, wherein said hard material layer is made of at least one material selected from the group of Nitrides, Carbides, Oxides, Carbonitrides, Oxinitrides, Oxicarbonitrides of Chromium and said intermediate layer is made of Chromium.
50. Tool or machine component, comprising:
- a base body of a metal or of a hard metal, and
- viewed in a direction from the base body towards an outside and at least along a part of said base body's surface, a hard material layer system having, as an outermost layer, a hard material layer, directly followed by an intermediate layer, latter directly followed by a sliding layer system, wherein said hard material layer is made of at least one Nitride of one of the following materials TiAl, CrAl, Cr, and said intermediate layer is made of said at least one metal.
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Type: Grant
Filed: Jul 23, 2004
Date of Patent: Jun 27, 2006
Patent Publication Number: 20050003241
Assignee: Unaxis Trading AG (Truebbach)
Inventors: Volker Derflinger (Feldkirch), Hans Braendle (Sargans), Christian Wohlrab (Feldkirch)
Primary Examiner: Archene Turner
Attorney: Crowell & Moring LLP
Application Number: 10/896,918
International Classification: B23B 27/00 (20060101);